Solar panels and solar boilers are increasingly being arranged commercially on roofs, which may or may not be pitched, in order to be able to employ solar energy in a relatively simple and advantageous manner for generating electricity or for heating a medium. Such objects are fixed to a roof by means of a fixing device or supporting device. The known fixing device herein comprises a plurality of profiles which are fixed by means of screws to one or more tile battens, and a mounting rail which is fixed to the profiles by means of, usually specifically designed, mechanical fixing elements, such as, for instance, bolts, nuts and the like. The actual object can be arranged on the mounting rail. The known fixing device does, however, have a number of drawbacks. A significant drawback of the known device is that the mounting of an object on the roof is a relatively time-consuming activity because of the relatively high number of mechanical fixing elements required. Special tools are often required, such as, for instance, a right-angle screwing machine, for mounting the device correctly. In addition, mounting of the device can usually only be carried out by specialist professionals, which generally makes mounting of the object relatively expensive.